Busy-test for multiple switchboards



(No Model.)

R. H. POLK.

BUSY TEST FOR MULTIPLE SWITOHBOAEDS. No. 527,393. Patented Oct. 9, 1894.

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UNITED STATES PATENT QFFICE.

ROBERT POLK, OF SAVANNAH, GEORGIA.

BUSY-TEST FOR MULTIPLE SWITCHBOARDS.

SPECIFICATION forming part of Letters Patent No. 527,393, dated October 9,1894.

Application filed April 20, 1894. Serial No. 508,357. (No model.)

To aZZ whom it may concern.-

Be it known that I, ROBERT H. POLK, a citizen of the United States, and a resident of Sayannah, in the county of Ohatham, State of Georgia, have invented certain new and usei f ul Improvements in Busy-Tests for Multiple to the accompanying drawings, and to letters of reference marked thereon, which form a part of this specification.

The invention is illustrated in the accompanying drawings as follows:

Figure 1,isaview in perspective of several sections of the switch-board, showing the improvements attached. Fig. 2 is a detail in longitudinal section of the test-plug showing its connections.

In the figures like reference marks indicate corresponding parts in all the views.

A is the switch-board of any usual or desired form.

B is the inclined shelf usually employed in upright switch-boards, and O is the head phone.

D are connecting cords of any desired construction and have plugs d on each end adapted to be inserted into the spring-jacks or line terminals of the switch-boards. Wires d are connected to each of these cords D intermediately and each is led to a condenser E composed of (say) six sheets of tin-foil having tissue paper sheets interposed and the whole inclosed by stiff cardboard or other insulation or stiffening. Alternate sheets of tin-foil of this pile are connected to a common conductor and one series thusmade is connected to the wire (1 aforesaid, while the other series or the other end of the condenser is connected to a wire (1 common to all condensers in all sections of the switchboard and leading to one end of the secondary of the induction coil F. The primary of this induction coil is in the circuit of a local battery f, and also included in said circuit is a wire it with the spring 71. which normally bears against the terminal h to which is connected the wire it which leads to the call wire 0. Said spring h is depressible by means of a button It extending through the casing h to within convenient reach of the thumb of the operator. Seated in the handle h near the end of the spring h and in a position to be contacted therewith is the terminal B of the wire '6 leading to a local battery I A spring h connected to the wire f extending to the secondary of the induction coil F and connecting with the side thereof opposite the wire (1 is also set within the handle and is provided with a button for depressing it with the forefinger of the operator. A terminal h is set in the handle h in a position to be contacted with by the spring 7L9 and a wire it connects it to earth. 7

The condenser is made of so few sheets of foil that no current other than the high voltage induced current will pass through it and hence the main battery current will not pass through, and cross-talk through the condenser, will not occur. The operation of this device is as followsz- When two subscribers are connected at one section of the switch board andacall is heard at another section thereof for one of the subscribers busy, the operator places the testplug H, in connection with the line number wanted by contacting the point 72 thereof with the spring-jack or line terminal bearing said number and presses the button 71, which gives her the tick (noting busy) in her head telephone through the wire 7L3, spring h, terminal k wire h and call wire a, the current for the tick coming, being the current indnced in the secondary of the coil F by the vibrated primary current from the battery f, taken to the li'nethrough the wire (1 the condenser E and the wires (1' and D, the latter being the loop connecting the subscribers line wanted, to the subscribers line busy,

in the other section of the switch-board. Pressing the button h as just mentioned completes the secondary circuit by sending its minus to the earth through the wires f 2 and h, connected through the terminals in and h in the plug H.

The test in this device produces a tick of absolutely the same loudness no matter how sorted in the working circuits.

long or short the line being tested and there is absolutely no retardation as nothing is in- It is obvious that the subscriber can only hear the tick when it is made in testing his line, and this may be prevented efiectually by duplicating the receiving instrument of the head telephone or by causing the test circuit to be entirely independent of the subscribers line in any manner. This system for busy-testing is applicable to both the magneto multiple and Law multiple systems of switch-boards. Having thus described my invention, what I claim-as new, and desire to secure by Letters Patent of the United States, is-

1. In a busy-test for multiple switch-boards, a high tension current source, a connecting loop, and a condenser of such capacity that the talking current will not pass through it, interposed in the'wire connecting said source I and loop, and a test-plug circuit, substantially as and for the purpose specified.

2. In a busy-test for multiple switch-boards, a local battery circuit including the primary of an induction coil and a test-circuit including the secondary of said inductioncoihthe subscribers line wire on the switch-board, a condenser through which the talking current cannot pass and an indicating device, for the purposes set forth.

3. In a busy-test for multiple switch-boards, the subscribers line on the switch-bo'ard,.a.

loop adapted to be inserted therein, a highvoltage circuit connected with said loop through a condenser having a high faradic capacity, and through which the talking current cannot pass and an indicator adapted to be operated by the current sent through said condenser, and a switch included in the aforesaid circuit, for the purposes set forth.

4:. In a busy-test for multiple switch-boards, the subscribers" lines connected thereto, a loop adapted to connect two of said subscribers lines, a condenser through whichthe talking current cannot pass, a wire connecting said condenser with said loop, a wire d ex- ROBERT H. POLK.

Witnesses: W. I. COGKQROFT, D. COLLINS. 

